Mine water and tailings overflow punish settling media in ways municipal clarifiers do not: abrasive solids, sudden flow changes, and pH that swings with the ore body. The selection rules below are the same ones we use when a plant asks us to size a retrofit.
Three things change the media choice, and none of them is about the media's nominal quality.
Solids load is high and variable. A clarifier handling a storm surge into an open pit, or a thickener overflow during a ore-type change, can carry several times its design solids for hours. Settling media does not stop working at high load — it fills. The question is how fast it recovers, and that is decided by cell size, not by surface area.
The solids are abrasive. Silica and ore fines polish polypropylene and, over years, will wear the leading edges of a plate pack. This is a service-life question, not a design question, and it is the reason stainless steel and FRP appear in mining specifications where they would be unnecessary in municipal work.
pH moves. Polypropylene is happy across the range a mine will present, but the reagent regime matters for the ancillaries — frames, anchors, fixings — far more than for the sheet itself. Ask what the pH range is and what it is dosed with, and get the answer in writing.
The published method does not change because the water is mine water:
| Settling area | Design flow ÷ hydraulic loading. Published loading for our settling media is 3–5 t/m²·h |
| Volume | Settling area × stacking height (published 4–5 m) |
| Channel velocity | Must stay in the 2.5–3.0 mm/s band; above it the flow in the channel is no longer laminar and more media will not fix it |
| Angle | 60° to the horizontal — steeper loses settling area, shallower stops the sludge sliding down the wall |
| Cell size | Φ25–90 mm; the range carries a specific surface of 62–236 m²/m³ and 93–97 % porosity |
Worked example: 3,600 m³/day is 150 m³/h. At 4 t/m²·h the settling area is 37.5 m². At a 4.5 m stack the net volume is 169 m³, which is 338 modules of 1000 × 500 × 1000 mm before any cutting allowance.
| PP (polypropylene) | Standard for most mine water. Published service life 3–4 years; co-polymer grades 8–10 years |
| FRP | Chosen where the specification calls for greater stiffness or where the pH range is outside what PP is normally asked to carry |
| Stainless steel | Chosen for abrasion and temperature rather than corrosion alone. Same published geometry as the PP range, different material — plate grade and service life are confirmed per project |
| Price | On request, against material, cell size, quantity and destination port |
We publish the geometry and the loading band because those are what a design is checked against. We do not publish a price list, because the same module in three materials is three different products.
Usually the larger end of the range. Tailings overflow carries a high and variable solids load, and a small cell blinds quickly. Take the cell that holds its velocity at the solids load you actually see, and confirm with the channel velocity check rather than choosing by removal efficiency alone.
It can raise the throughput of the clarification area you already have, which is what most retrofits are for. What it cannot do is change the settling behaviour of the solids: if the particles need flocculant, they still need flocculant. Media buys you area in a smaller footprint, not a different chemistry.
The symptom is a rising sludge blanket and falling overflow clarity at the same flow and the same dose. Inspect the upstream face of the pack during a shutdown: if the first 100 mm is loaded and the rest is clean, the problem is upstream of the media, in pre-treatment or flocculation.
Send the specification and we will state which clauses we can meet and which we cannot. We do not claim compliance with a standard we have not been assessed against; if the project needs a certificate of conformity from a named body, raise it at enquiry stage and we will tell you honestly whether it is achievable.
Flow, solids load, pH range and the plan of the existing basin. We return the cell size, the volume and the material options, with the assumptions written down.
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